This invention relates to supported catalysts containing titanium and magnesium. In one aspect this invention relates to catalysts useful for the polymerization of olefins. In a more specific aspect the present invention relates to catalysts useful for the polymerization of polypropylene.
A number of supported catalysts containing titanium and magnesium are known, for example, U.S. Pat. No. 3,787,384 discloses one in which a support of silica, alumina, or a mixture thereof is contacted with either a hydrocarbyl magnesium, a hydrocarbyl halogen magnesium, a hydrocarbyl aluminum, or a hydrocarbyl hydrogen aluminum compound, followed by an excess amount of a halogen compound of a transition metal.
U.S. Pat. No. 3,993,588 is another which discloses preparing a catalyst component by contacting silica with a magnesium compound and by contacting the resulting component with a titanium compound.
U.S. Pat. Nos. 4,458,058 and 4,258,159, the disclosures of which are incorporated herein by reference disclose preparing catalysts by contacting a transition metal compound with a porous aluminum oxide support which had been contacted with a magnesium compound.
Commonly owned, recently issued U.S. Pat. No. 4,855,271, the disclosure of which is incorporated herein by reference, discloses a still more unique type of supported catalyst containing titanium and magnesium. The catalysts disclosed in that patent are prepared by contacting a support comprising highly porous aluminum oxide containing a magnesium compound first with an alcohol and then subsequently with a halide, alkoxide, or haloalkoxide of titanium. While these catalysts have proven to have desirable properties particularly in the production of polymers from ethylene, they have not been found to be as commercially useful for the production of crystalline polypropylene by the polymerization of propylene. In the polymerization of propylene, it was found that the catalysts were not as active nor as selective to the hydrocarbon insoluble crystalline polypropylene as might be desired.
An object of the present invention is to provide a new catalyst with improved selectivity for the production of crystalline polypropylene.
Another object of the present invention is to provide a new type of catalyst which is capable of also providing a desirable balance of productivity and selectivity.